This invention relates generally to color cathode ray tubes of the type having a shadow mask, and more particularly to structures for suspending a shadow mask in a color tube and for referencing the color tube faceplate to its associated funnel. The invention is especially concerned with an improved stud comprising part of each of a plurality of mask suspension devices and also part of a faceplate-funnel referencing system.
Conventional color cathode ray tubes have a glass envelope which comprises a flanged front panel sealed to a funnel. A shadow mask is supported adjacent to a phosphor screen pattern deposited on the inner surface of a faceplate portion of the front panel. The mask is supported on studs embedded in the inner surface of the front panel flange. A neck for housing electron guns for the tube is sealed to the funnel.
Proper tube operation requires that the shadow mask be suspended at a precise distance from the phosphor screen pattern and at a precise orientation relative thereto. Proper tube operation also requires that the phosphor screen pattern and the aperture pattern in the associated shadow mask be aligned with respect to the effective source of electron beams in the assembled tube in the same way that they were aligned with respect to an effective point light source used to screen the phosphor pattern on the faceplate. If this corresponding relative alignment is not established, color purity errors will inevitably be exhibited in the images displayed by the end-product tube.
This invention is especially useful when embodied in a novel type of shadow mask color tube having a flangeless faceplate on the inner surface of which is suspended the shadow mask. This novel tube has a lightweight, frameless, torsionally flexible shadow mask which is supported by four suspension devices-- one at each corner of the mask.
This suspension arrangement has a number of unique requirements which are not imposed on conventional mask suspension systems, including the requirement that because of their corner location, such suspension devices must be particularly compact so as not to require an undesirably large tube envelope.